Energy

Chapter 5

What is Work?

Work occurs when a force acts upon an object in the direction of the force applied

If you push against a wall and the wall doesn’t move, have you done any work?

Unit is the Joule (J)

What is Energy?

The ability to do work Unit is the Joule (J) Energy can be transferred from one object to

another

Reflect

What do you think of when you think of energy? Draw a picture of what energy means to you.

Kinetic Energy Energy of motion Kinetic Energy depends on speed and mass Kinetic energy = mv2

2 m is mass, v is speed (velocity) Speed has more of an effect on kinetic

energy than mass does because speed is squared.

Reflect

Draw a picture of something that has kinetic energy

Do the math:A 200 kg car is travelling at a speed of 10

km/hr. What is the kinetic energy of the car? Show all work

Potential Energy

Energy of position or shape

Ex.- the bow is not moving, but it has potential energy because work was done to change its shape

Gravitational potential energy

Energy due to an object’s position above the earth’s surface

The amount of energy is determined by the object’s weight and its distance above the earth’s surface

Gravitational potential energy = weight x height

Reflect

Draw a picture of something that has gravitational potential energy

Do the math:A toy is 40N and is on a shelf that is 10 meters

above the floor. What is the gravitational potential energy of the toy?

Show all work

Mechanical Energy

Total energy of motion and position of an object

Mechanical energy = potential energy + kinetic energy

Reflect

Do the math:A ball has a potential energy of 5 joules at the

highest point of a bounce and a kinetic energy of 25 joules while the ball is moving. What is the total mechanical energy of the ball?

Show all work

All forms of energy can be categorized as either kinetic or potential

PotentialStored energyEnergy of positionChemicalNuclearStored MechanicalSound

Kinetic Energy of motion Waves, electrons,

atoms, molecules, and substances

Radiant Thermal Motion Sound Electrical

Matter

All matter is made up of particles in motion. Because the particles are in motion, they have kinetic

energy. At higher temperatures particles move faster and

therefore have more kinetic energy.

 

Reflect Draw pictures of the molecules in ice,

water and steam in the boxes and answer the questions

Which has the most energy – ice, water, or stream?

Which has the least energy – ice, water, or steam?

Thermal Energy The total internal energy of the particles that make up an object. The vibration and

movement of atoms and molecules within the substance. The faster the particles move, the more thermal energy they have The bigger the object is, the more thermal energy it has because there are more

molecules that move Geothermal energy is an example of thermal energy

Reflect

Name 3 things that have a little bit of thermal energy

Name 3 things that have a lot of thermal energy

Which has more thermal energy – the ocean or a lit match?

Chemical Energy

Energy of a compound that changes as the atoms are rearranged

Form of potential energy The more atoms that are bonded together in a

compound, the more potential energy that compound has

Energy stored in the bonds of atoms: Biomass, petroleum, natural gas, propane and coal are

examples Food also has chemical energy

Photosynthesis uses light energy to make sugars

Plants absorb the light in their leaves and change it to chemical energy

When we eat, we absorb the chemical energy

Reflect

Circle where you would find chemical energy

H

O

H Cl Cl

Electrical Energy The energy of moving electrons Lightning and electricity Electricity is by the changing position of

magnets so it can be considered a form of potential energy

When you plug something in electrons move back and forth transferring energy so it is a form of kinetic energy

Electrical energy is produced at power plants and then transferred to your home

Source: http://www.eia.doe.gov/kids/energyfacts/sources/electricity.html#HowIsATransformerUsed?

Reflect

List 5 things you use daily that use electricity

Sound Energy

Caused by an object’s vibrations Sound is the movement of energy through

substances in longitudinal waves Is both potential and kinetic To make an object vibrate, work must be done You change the shape therefore you create

potential energy When released, air particles are moved creating

kinetic energy

Sound waves cause air to vibrate which transmitenergy

Reflect

Write a short song about sound energy to the tune of Mary Had a Little Lamb

Light (Radiant) Energy

Radiant energy is electromagnetic energy that travels in transverse waves Light energy is an example of radiant energy Light energy is made up of photons which are little packets of energy Part of the electromagnetic spectrum

Electromagnetic Waves have different wavelengths

When you listen to the radio, watch TV, or cook dinner in a microwave oven, you are using electromagnetic waves.

Source: http://imagers.gsfc.nasa.gov/ems/waves3.html

                         

                             

Radio waves, television waves, and microwaves are all types of electromagnetic waves. They only differ from each other in wavelength. Wavelength is the distance between one wave crest to the next.

Source: http://imagers.gsfc.nasa.gov/ems/waves3.html

Waves in the electromagnetic spectrum vary in size from very long radio waves the size of buildings, to very short gamma-rays smaller than the size of the nucleus of an atom.

Reflect

Put the following in order of wavelength starting with the shortest and ending with the longest: Infrared; TV; X-rays; AM Radio; Visible light; Microwave

Nuclear Energy

The energy within the nucleus of an atom Two types:

Fusion – this is done by the sun. It is when the nuclei of atoms are fused together thereby releasing a huge amount of energy

Fission – this is done by nuclear power plants. It is when the nuclei of an atom is broken apart thereby releasing a huge amount of energy

Is this Fusion or Fission?

Reflect

Is this Fusion or Fission?

List two good things about nuclear energy

List two bad things about nuclear energy